Association between timing of hoof trimming in primiparous cows and hoof health and survival in second lactation

Lameness in dairy cows, primarily caused by claw lesions, generates significant welfare and economic challenges. Hoof trimming is a key preventive measure, with scientific support for 2 to 3 trimmings per lactation. However, the optimal timing of these trimmings has not yet been fully explored. This retrospective cohort study aimed to investigate the association between timing of 2 hoof trimmings during first lactation and subsequent hoof health and culling in second lactation. Data from 10,349 primiparous cows across 185 Swedish dairy herds (2015-2018) were analyzed. Multivariable mixed-effect logistic (models L1 and L2) and multinomial logistic regression models (models ML1 and ML2) assessed associations with hoof health in early second lactation (within 90 DIM) and survival during second lactation (within 300 DIM). Explanatory variables included timings of the first and second trimmings, interval between trimmings, hoof health at trimming, and breed. Herd was incorporated as a random effect or cluster to account for herd-level variations. The L1 model indicated that most trimming combinations other than a late first trim (>120 d after calving) coupled with a late second trim (<61 d before calving) significantly reduced the odds of claw lesions. However, the ML2 model showed that the association varied somewhat depending on the type of claw lesion found. The L2 model generally displayed lower odds of culling (dead, euthanized, and slaughtered) for cows trimmed early in first lactation and further from second calving than 60 d. Although the ML2 model revealed no association between timing of trimming and mortality (dead and euthanized), it did find a significant association with being sent to slaughter. In summary, strategic timing of hoof trimming, early in first lactation and well before second calving, can improve hoof health and survival in dairy cows and consequently have the potential to improve animal welfare and sustainability within the dairy sector.